Someone said you could convent a 40 into a 10mm. I questioned that.
Never heard of nuns in the convent "converting" their .40 pistols to 10mm, but I suppose anything's possible.
Seriously, though, in the past there've been numerous threads on various boards on how to do a .40--->10mm conversion on certain makes/models of .40 pistols, provided that the .40 magazine was, or could be made, compatible with the COAL of the 10mm.
For example, the old Mauser M2s in .40. These were also made in .45acp, but the mag well dimensions were the same. Ambitious owners discovered you could have a 'smith ream out the .40 chamber to 10 specs, and then use the .45acp M2 mags for the 10mm cartridges, once you tweaked (narrowed) the feed lips a bit. Since breech-face dimensions for the .40 cartridge are the same as for 10mm, the M2's extractor and ejector worked fine. Posters who did this conversion also mentioned upgrading the M2's f.p. & recoil springs with Wolff XPs.
Years ago, on the old Pistolsmith board, there were several threads running on .40--->10mm conversions on makes of pistols never made in 10mm by the factory. The M2 was one. Another was one of the HK .40 models - I forget which, but it was probably the full-size .40, not the compact. Anyway, the basic conversion process was similar. Try your google-foo if you want more info.
About this time (say, early-to-mid 2000s), there was interest in converting Sig .45acp P220s to 10mm. Master pistolsmith Bruce Gray (of GrayGuns) found that a reliable and durable conversion was feasible, but only on
stainless P220s. He began converting quite a number of these to 10mm (using a new 10mm barrel - from Bar-Sto, I believe) on customer-supplied SS 220s and their magazines. And although quite pricey, his work was fabulous, judging by the resulting on-line reviews. These Gray-converted 220s ran fine in 10mm.
It was several of these Gray 220s that Sig obtained and examined in later deciding to produce a factory 10mm P220, ... four of them actually.
Also, since we're on the subject can you produce peer reviewed evidence that of this statement?: "It's bad enough the .40 S&W has become the most Kaboom!-prone auto cartridge ever invented"
Dude, google-foo is your friend.
